<!DOCTYPE html>
<html lang="en">
<head>
    <meta charset="UTF-8">
    <title>focus伪类选择器</title>
  <style>
    input:focus {
      background-color: pink;
      color: red;
    }
  </style>
</head>
<body>
<input type="text">
<input type="text">
<input type="text">

</body>
</html>